In many applications, a door is used to secure access to a confined storage space. Hence forth, any door, lid, or cover is hereafter referred to as a door. In certain applications, the door acts as a seal isolating the storage space from the environment. In these applications, a heavy door is used as a structural reinforcement and also as a natural barrier. It is also particularly beneficial where cleanliness is a concern. Some examples are shown in FIG. 1A-1E.
In FIG. 1A the door 0101 is horizontal when closed indicated by position 0111. A handle is not shown on this or most of the other figures as it is immaterial to the current invention. The door is hinged or pivoted about point 0102. The method of fixing the hinge to the door is not shown and is immaterial to the current invention. Also, the position of point 0102 relative to the door is not identified as it too is immaterial to the present invention. The door 0111 when closed sits on a top panel 0121, 0122, and 0123. The position 0122 is an opening in the panel that is revealed when the door is opened.
Often it is required for the door to remain closed under its own weight if there are no external forces. Thus, the present invention applies when the door, when closed, is:                horizontal as shown in FIG. 1A,        slopes down as shown in FIG. 1B        slopes up as shown in FIG. 1C        
The present invention applies when the door, when closed, is:                sitting on the top panel as shown in FIG. 1A        partially recessed from the top panel as shown in FIG. 1D        recessed from the top panel as shown in FIG. 1E        
In all subsequent figures, it is assumed that the door is shown as horizontal when closed and sitting on top of the panel as indicated in FIG. 1A. Further, it is assumed that the ideal opening for the door is 90°, but the present invention applies to any degree of opening that is reasonable to permit access to the opening. The subsequent FIG.s and descriptions use these two assumptions for brevity but this must not be construed to restricting the applicability of the present invention.
The typical way to accomplish the objective is with one or two gas struts as shown in FIG. 2. The door 0201 pivots at one or more hinges 0202 and is accessed by handle 0203. The gas strut 0204 is selected so that once the door is open past position 0205 that the force of the gas strut will continue to open the door until the strut has reached its end stop. The opening 0206 is now accessible.
To close the door, the operator pulls against the force of the gas strut; the weight of the door helps the user. As the door closes, the weight of the door overcomes the force of the gas strut and the door closes fully. This approach has worked well for years, but has several disadvantages:                the gas strut is in the way of the opening exposed by the door        the fasteners used for mounting gas struts may loosen over a period of time requiring extra maintenance        it is difficult to keep the fitting for the gas strut and fasteners completely clean        the gas strut and fasteners may come in contact with the working environment which may become hazardous for the operation; for example, if the machines are used in food processing or pharmaceutical manufacturing        
Alternative methods can use a special hinge. There are two main types of special hinges: the torque hinge and the self-closing hinge.
For a torque hinge, this provides a constant torque in the opening direction and a constant torque in the closing direction. These two torque values may be the same or different (resulting in an asymmetric torque hinge). The asymmetric torque hinge may be preferred. It is shown in FIG. 3. The door 0301 has one or more hinges 0302. This type of hinge usually requires that it is mounted flush with the upper surface of the door so the hinges are supported by block 0303. The door covers the opening 0306.
The characteristics of the hinge are shown in FIG. 4. The FIG. shows the torque of the hinge from 0° (closed) to 90° (fully open) and back again. Along path 0401 the torque is low as the door is opened. When the door is open the path 0402 shows a higher torque required to close the door. The torque required to keep the door open (shown as 0403) is proportional to cos(ø) where ø is the angle of opening (assuming the door is horizontal when closed). This curve reflects the distance of the center of mass of the door from the hinge point.
Where the line 0403 intersects line 0402 indicates the angle at which the door will be held by the hinge (to the right of the intersection) or where it will fall under its own weight (to the left of the intersection). This point is marked as 0404 on FIG. 4 and it is reasonably desired that this angle is about 30°.
This type of hinge allows the user to easily open the door. The low torque 0401 in FIG. 4 is shown as 0304 in FIG. 3. The higher closing torque of 0402 in FIG. 4 is shown in means that the door will stay open. When the user closes the door, the weight of the door assists in overcoming the torque. There are three problems:
(i) The door, being heavy, is hard to open. The assistance of the gas strut that was used in FIG. 2 is missing. This can be overcome with the addition of one or more extension springs and there exist specific torque hinges on the market constructed like this. Alternatively, one or more separate extension springs 0307 can be positioned for example as shown in FIG. 3.
(ii) The torque hinge is resisting the closing of the door. [This is easily seen on the display of a laptop computer. When the display is open, if you move the end of the display just a few mm, it will return to its original position. Making the laptop display close completely is difficult and many earlier models would leave the display slightly open by a few mm.] With this type of hinge it is impossible to close the door completely and it will remain open a few mm. This can be overcome by the addition of a latch installed at the front of the door to hold the door closed. However, it is an objective of the present invention that a latch should not be present as this adds to the disadvantages of the current state of the art as described above.
(iii) As the door closes, the torque that the door presents on one side of the hinge results in a reactionary torque (equal and opposite) on the other side of the hinge. This results in a force pushing the hinge down and thereby rotating its mounting plate as the door is closed. This is shown in FIG. 7 which is a side view.
(iii)(a) In FIG. 7A, the hinge 0702 is connected to the door 0701. The hinge is mounted on the top panel 0711, 0712, and 0713. The part 0712 is the opening that the door 0701 covers. The door is closed in the direction 0703.
(iii)(b) FIG. 7B shows what happens as the door is closed. The force 0723 on door 0721 results in a torque 0722 about the back of the panel 0730. The top panel (0731, 0732, and 0733) deforms while force 0723 is applied. The door rests on the top panel, but the angle 0725 (representing the angle of the door from the vertical position) is greater than 90°.
(111)(c) FIG. 7C shows the effect after the force 0723 is removed. With the force 0723 removed, the top panel reverts to its original shape (as shown in FIG. 7A). The angle 0745 is identical to 0725 and this results in the door remaining partially open.
For the self-closing hinge, it presents minimal toque to open or close the door. It has a damper mechanism on closing so it allows the door to close on its own slowly. This hinge is commonly used on toilet seats. This type of hinge is installed the same way as the torque hinge shown as 0302 in FIG. 3. The torque characteristics are shown in FIG. 5. The hinge allows the user to easily open the door (low torque as indicated as 0501). The torque required to hold the door is shown as 0503 which intersects the line representing the closing torque (0502) close to the fully open position (90°). As soon as the door is moved from this position the door starts to close because its weight overcomes the torque of the hinge and the door closes. The damper in the hinge causes the door to close slowly.
There are two problems with this type of hinge:
(i) The hinge will not hold the door open at any angle. It must be opened nearly 90° or more to ensure it will not fall back to the closed position. This means that it requires a support to hold it just past the vertical point. The support structure is undesirable in most situations and it can be inconvenient to have to open the door so far.
(ii) Users may want to close the door themselves. They will try to overcome the damping force in the hinge. With current technology, the life of these hinges is about 10,000 cycles and forcing the door closed will reduce the life of the hinge.
It is apparent that the use of readily available technologies to solve the problem cannot be deployed.